The present invention relates to a method of analyzing a DSC curve for accurately acquiring a freezing point of a sample showing supercooling by differential scanning calorimetry, and a method of carrying out temperature calibration in cooling of a differential scanning calorimetric apparatus by using a sample evaluated with a freezing point.
In differential scanning calorimetry of a background art, a freezing point of a sample showing supercooling is not acquired, or a crystallizing temperate is read as shown in FIG. 2 of Nonpatent reference 1 (see below) and Nonpatent Reference 2 (see below).
Nonpatent Reference 3 (see below) shows a method of measuring an evaluated freezing point of a sample by a crucible method as a temperature calibrating method of a thermocouple. A freezing point is measured by inserting a thermocouple directly into a sample, and therefore, when a temperature of the sample is made to be constant at a freezing point, a temperature curve shows a horizontal flat region, and therefore, it is known that the temperature may be read as it is.
Nonpatent Reference 4 (see below) shows an example of measuring a freezing point by a crucible method by directly inserting a thermocouple similarly into a sample of lead free solder. In order to firmly measure a flat region, an amount of the sample is an extraordinary large amount in comparison with that in differential scanning calorimetry.
[Nonpatent Reference 1] Japanese Industrial Standards JIS K 7121: 1987 transition temperature measuring method of plastic (paragraphs 4-5, FIG. 2, example of method of acquiring crystallizing temperature)
[Nonpatent Reference 2] ISO 11357-1: 1997 Plastics-Differential scanning calorimetry (DSC)-Part 1: General principles page 33. 10 characteristic temperatures, Page 5, 8. 2 Temperature calibration
[Nonpatent Reference 3] Japanese Industrial Standards JIS C 1602: 1995 thermocouple (paragraph 44, reference 2 FIG. 1)
[Nonpatent Reference 4] Japanese Industrial Standards JIS Z 3198-1: 2003 lead free solder testing method-part 1: melting temperature range measuring method
According to the freezing point temperature measuring method in differential scanning calorimetry of a background art, as shown by FIG. 2 of above Nonpatent Reference 1, the crystallizing temperature is read, however, according to the method, with regard to a case of a sample showing supercooling, a temperature in correspondence with a temperature of staring to freeze a supercooled liquid is read, the temperature is a temperature which differs from the freezing point.
Further, although according to a method other than the differential scanning calorimetry, there is a method of measuring a temperature by directly inserting a thermocouple to a sample, in view of a structure of a differential scanning calorimetric apparatus, the thermocouple cannot directly be inserted into the sample and also an amount of the sample which can be installed in the apparatus is limited. Therefore, a systematic error by a heat flow is produced in a temperature measured value, and it is difficult to realize a stable freezing procedure over a long period of time since the sample amount is small.
It is a problem of the invention to provide a method of analyzing a DSC curve, an output temperature curve for acquiring an accurate freezing point from a result of differential scanning calorimetry and a temperature calibrating method in cooling a differential scanning calorimetric apparatus even in a sample showing supercooling.